Sanctify unto me all the firstborn, whatsoever openeth the womb among the children of Israel, both of man and of beast: it is mine. Sanctify unto me all the first-born - To sanctify, קדש kadash, signifies to consecrate, separate, and set apart a thing or person from all secular purposes to some religious use; and exactly answers to the import of the Greek ἁγιαζω, from a, privative, and γη, the earth, because every thing offered or consecrated to God was separated from all earthly uses. Hence a holy person or saint is termed ἁγιος, i.e., a person separated from the earth; one who lives a holy life, entirely devoted to the service of God. Thus the persons and animals sanctified to God were employed in the service of the tabernacle and temple; and the animals, such as were proper, were offered in sacrifice.
The Hindoos frequently make a vow, and devote to an idol the first-born of a goat and of a man. The goat is permitted to run wild, as a consecrated animal. A child thus devoted has a lock of hair separated, which at the time appointed is cut off and placed near the idol. Hindoo women sometimes pray to Gunga (the Ganges) for children, and promise to devote the first-born to her. Children thus devoted are cast into the Ganges, but are generally saved by the friendly hand of some stranger - Ward's Customs.
Whatsoever openeth the womb - That is, the first-born, if a male; for females were not offered, nor the first male, if a female had been born previously. Again, if a man had several wives, the first-born of each, if a male, was to be offered to God. And all this was done to commemorate the preservation of the first-born of the Israelites, when those of the Egyptians were destroyed.